In the construction industry, a tool in the form of an adjustable T-square is desirable, particularly for cutting wall board. Such a T-square should have a blade and cross member with the cross member being easily adjustable to various angular positions and various positions along the longitudinal axis of the blade. This adjustment facilitates making angular cuts in the wall board and locating openings in the wall board for devices such as electrical outlets and switches.
Conventional adjustable T-squares, for the most part, are intended merely as drafting instruments. These drafting instruments are not adaptable or easily usable in forming large tools suitable for use in the construction industry.
For example, U.S. Pat. No. 3,273,246 to Siberini discloses an adjustable T-square having a blade and a cross member coupled for longitudinal and angular adjustment. A thumb screw passes through a longitudinal slot within the blade and is engaged in a threaded aperture within the cross member. The blade is received on one surface of the cross member to permit angular adjustment and on the opposite surface to permit longitudinal adjustment. For longitudinal adjustment, the blade and head are coupled by a dovetail arrangement requiring the thumb screw to be completely removed and the blade to be axially removed from the cross member notch to change from the sliding motion with the cross member maintaining a perpendicular relationship relative to the blade to the angularly adjustable position. The Siberini T-square requires the head member to be located in only one position along the longitudinal length of the blade to permit use of its angular indicia.
In another example, U.S. Pat. No. 905,249 to Townsend discloses an adjustable T-square having two threaded members. Each of these threaded members must be adjusted to vary the angular and/or longitudinal position of the cross member.
U.S. Pat. No. 2,435,529 to Brockley and U.S. Pat. No. 2,545,112 to Sheridan disclose adjustable T-squares having pin and hole arrangements for angularly adjusting a cross member relative to its blade.
U.S. Pat. No. 506,416 to Colley discloses an adjustable T-square having a cross member with a notch receiving its blade. When the blade is received within the notch it is maintained perpendicular relative to the blade. Angular adjustment is permitted by removing the blade from the notch and pivoting the blade relative to the cross member to the desired angle. A threaded connection locks the blade within the notch or secures the blade against the back surface of the cross member to maintain the blade and cross member at the desired angle. However, the cross member cannot be located in an adjusted position the length of the blade by the threaded connector.